Supplemental Financial Information

Supplemental Balance Sheet Information

The following table summarizes the components of Prepaid expenses and other assets and Other long-term assets, net as presented in the Condensed Consolidated Balance Sheets:



	As of
(in thousands)	March 31, 2020		December 31, 2019
Prepaid expenses and other assets:
Prepaid expenses	$	1,592	$	1,708
Prepaid income taxes	4,772		4,228
Other	1,241		1,896
	$	7,605	$	7,832
Other long-term assets, net:
Right of use assets, operating leases, net	$	4,358	$	5,073
Spare parts, net	3,360		3,453
Mine development costs, net	7,457		7,084
Mine reclamation asset, net	2,423		2,451
Highview Investment	552		552
Other long-term assets	1,842		1,718
	$	19,992	$	20,331

Spare parts include critical spares required to support plant operations. Parts and supply costs are determined using the lower of cost or estimated replacement cost. Parts are recorded as maintenance expenses in the period in which they are consumed.

Mine development costs include acquisition costs, the cost of other development work and mitigation costs related to the Company's mining operations and are depleted over the estimated life of the related mine reserves, which is 21 years. The Company performs an evaluation of the recoverability of the carrying value of mine development costs to determine if facts and circumstances indicate that their carrying value may be impaired and if any adjustment is warranted. There were no indicators of impairment as of March 31, 2020. Mine reclamation asset, net represents an asset retirement obligation asset and is depreciated over the estimated life of the mine.

The Company holds a long-term investment (the "Highview Investment") in Highview Enterprises Limited ("Highview"), a London, England based developmental stage company specializing in power storage. In November 2014, the Company acquired an 8% ownership interest in the common stock of Highview for $2.8 million in cash. The Company accounts for the Highview Investment as an investment recorded at cost, less impairment, plus or minus observable changes in price for identical or similar investments of the same issuer.

The Highview Investment is evaluated for indicators of impairment such as an event or change in circumstances that may have a significant adverse effect on the fair value of the investment. There were no changes to the carrying value of the Highview Investment for the three months ended March 31, 2020 as there were no indicators of impairment or observable price changes for identical or similar investments.

The following table details the components of Other current liabilities and Other long-term liabilities as presented in the Condensed Consolidated Balance Sheets:



	As of
(in thousands)	March 31, 2020		December 31, 2019
Other current liabilities:
Current portion of operating lease obligations	$	2,142	$	2,382
Accrued interest	298		213
Income and other taxes payable	805		678
Other	1,030		1,038
	$	4,275	$	4,311
Other long-term liabilities:
Operating lease obligations, long-term	$	2,415	$	2,810
Mine reclamation liability	2,752		2,721
Other	71		229
	$	5,238	$	5,760

Supplemental Condensed Consolidated Statements of Operations Information

The following table details the components of Interest expense in the Condensed Consolidated Statements of Operations:



	Three Months Ended March 31,
(in thousands)	2020		2019
Interest on Senior Term Loan	$	630	$	1,270
Debt discount and debt issuance costs	354		381
453A interest	132		322
Other	94		131
	$	1,210	$	2,104